Replaceable acoustic absorber for internal combustion engine detonation suppression



July 12, 1955 A. G. BODINE, JR 2,712,816 REPLACEABLE ACOUSTIC ABSORBER FOR INTERNAL COMBUSTION ENGINE DETONATION SUPPRESSION Filed Sept. 8, 1952 IN V EN TOR. 445527 6. Boo/NE J2 United States Patent ()fifice 2,132,315 Patented July 12, 1955 REPLACEABLE ACOUSTIC ABSORBER F012 IN- TERNAL CGMBUSTEQN ENGINE DETONATION SUPPRESSION Albert G. Bofine, in, Van Nuys, Calif. Application September 8, 1952, Serial No. 308,331 9 Claims. (Cl. 123191) This invention relates generally to internal combustion engines and to means for suppressing irregular burning and detonation of fuel-air mixtures in internal combustion engines. The present application is directed to improvements in the field covered by my Patent No. 2,573,536, issued October 30, 1951, and entitled Engine Detonation Control by Acoustic Methods and Apparatus. For a full disclosure of the acoustic aspects of detonation in combustion, and my basic solution for controlling detonation in combustion, reference should be had to my said Patent No. 2,573,536.

The present invention is based on the now known fact that detonation in an engine combustion chamber produces sound waves, a large part of which rise to high amplitude at resonant frequencies of the chamber, and on my discovery that various well known and harmful manifestations of detonation. According to my basic invention, I control, stop or attenuate these harmful efiects by interfering with or attenuating the high amplitude detonation-induced sound waves, and this is done by use in connection with the combustion chamber of acoustic attenuation means made responsive to the frequencies at which the detonation-induced sound waves tend to appear at high amplitudes.

The general object of the present invention is the provision of an improved simple type of acoustic attenuator combined in a novel form and arrangement with the combustion chamber of an internal combustion engine.

A further object is the provision of such an improved type of acoustic attenuator, characterized further by easy accessibility for clean-out or servicing.

A still further object is the provision of a sound wave attenuator of simple form, positioned in a particularly strategic position in the combustion chamber for control of the offensive detonation sound wave patterns prevalent within the chamber.

The invention will be best understood from the following detailed description of one present illustrative embodiment thereof, reference for this purpose being had to the accompanying drawings, in which:

Figure 1 is a longitudinal sectional view through the combustion chamber portion of an engine block equipped with the present form of the invention;

Figure 2 is a section taken on line 22 of Figure 1;

Figure 3 is a detailed section taken on line 33 of Figure 2; and

Figure 4 is a longitudinal sectional view of the re placeable attenuator element removed from the engine.

In the drawings, numeral designates a water-cooled engine block for a valve-in-head type engine, and numeral 11 designates the water-cooled head for said engine. Block 10 has cylinder 13, in which is fitted the piston 12. The head 11 is shown to have a generally domed combustion chamber 14, equipped with intake and exhaust valves 15 and 16, respectively, and with a spark plug 17. Suitable gear for operation of the valves is these sound waves produce the 6 2 indicated at 18. A gasket 19 is shown between the opposed surfaces 20 and 21 or" the block and head.

A long arcuate recess 22 is sunk into the surface 21 of the head, and extends generally circumferentially about and just outside the perimeter of the combustion chamber for a substantial distance, preferably through a central angle of about 90 or greater. At one end this recess is tilted upwardly, and extends as a bore 22a out through the side wall of the head to a conveniently accessible location. The outer end of this bore 22a is counterbored and tapped for a hex-headed screw 23 formed with a recess 24.

Between the recess 22 and the combustion chamber 14 is an arcuate shallower recess 25, forming a constricted sound wave communication passage between the combustion chamber and recess 22 throughout the arcuate extent of the latter. With the block and head in assembly, the recess 25 will be seen to form a ledge facing and spaced a short distance from gasket 19, providing a narrow slot or constricted neck passage between the chamber 14 and the arcuate recess 22, extending the full length of the recess 22. In a typical installation, the slot or passage formed by the recess 25 may be of the order of A in vertical thickness.

Lodged in the recess 22 is a longitudinally extended acoustic absorber 30, absorbent material capable of attenuating sound waves which enter the recess 22 via the narrow slot or passage 25. In the present illustrative embodiment, this sound wave absorber 39 comprises an elongated body of absorptive material 31 such as fiber glass, provided with porous loom casing 32 of some suitable material such as woven fiber glass, or metal mesh such as is used for cable shielding. The body is stifiened by means of a longitudinally extending resilient member 33 such as piano wire, having molded onto opposite ends suitable beads 34 and 35, preferably of a suitable ceramic. The casing 32 will be beads 34 and 35, and the whole is stiffened by the wire 33, though the body as so formed will be appreciated to have a substantial degree of resilient flexibility. The end of the wire 33 protrudes beyond the bead 35 to furnish a handle 36.

The absorber 39 is inserted into the recess 22 through the bore 22a, screw 23 being first removed. The absorber may substantially fill the cross section of the recess 22, as illustrated in Figure 1, though this is not in all cases necessary, since some chamber space may be permitted around the outside of the absorber. The handle part 36 is received within the hollow of the screw 23 when the parts are in assembly, and when the screw 23 is removed, the handle part 36 may easily be grasped by means of a pair of pliers, and the absorber withdrawn. The absorber is thus easily installed, and easily removed for servicing or replacement. For ease of removal, I have found it desirable to use a loom 32 woven with a diagonal weave so that it tends to become smaller in diameter when pulled axially. This tends to break it loose from carbon and varnish formed in the groove 22 by combustion deposit. It is also quite easy to clean out the passage with a flexible, elongated wire brush, before re-installing a new attenuator.

In operation, a detonation pressure wave initiated within the combustion chamber of the engine, above the piston, causes sound wave transmission through the slot 25 into the recess 22, and upon encountering the acoustic absorber body 30, the sound wave so transmitted is eifectively absorbed and attenuated, its energy being converted into heat.

A resonant absorber body composed of such a substance as fiber glass or the like is known to have a degree of response selectivity to a particular sound wave freseen to be stretched between the twoquency or frequency range, though the degree of selectivity is nowhere near as marked as with highly resonant devices such as Helmholtz resonators or quarter-wave pipes, for example. Nevertheless, it is generally desirable to design the acoustic body, in accordance with well known acoustic techniques, to have its principal response frequency range in good correspondence with the detonation frequencies encountered in a particular engine. It is of course known that combustion chambers have various resonant frequencies and various modes of gas oscillation, and that these depend in any given case upon the particular combustion chamber design. In the practice of the invention, therefore, the frequencies at which resonant peaking of sound wave tends to occur can be readily ascertained by known acoustic technique, and the absorber body is then designed so that the sound wave frequencies of the engine which are to be attenuated come within the principal response-range of the absorber.

. chamber, so as to afford assurance of coming into intimate relationship with one or more pressure antinode regions within the chamber, whether or not the location of such pressure antinode regions has been accurately determined. Such an intimate coupling of the absorber to one or more pressure antinodes of the chamber creates a condition which is highly destructive of the detonation wave pattern. t

The attenuator of the invention thus has the advantage of being located in close coupled relationship to regions within the chamber where detonation induced sound wave patterns can be readily attacked. It has the further advantage of ease of initial installation, and ease of subsequent servicing and replacement.

It will be understood that the drawings and description are illustrative only and that various changes in design, structure and arrangement may be made without departing from the invention as defined by the appended claims.

I claim:

1. Detonation suppression means for an internal combustion engine comprising, wall means forming a combustion chamber, said wall means formed with an elongated recess disposed closely adjacent to said combustion chamber for a substantial distance and communicating with said chamber via a sound wave passage for a substantial proportion of said distance, and an elongated sound wave absorptive body lodged in said recess.

2. Detonation suppression means for an internal combustion engine comprising, wall means forming a combustion chamber, said wall means formed with an elongated recess disposed closely adjacent to said combustion chamber for a substantial distance and communicating with said chamber via a sound wave passage for a substantial proportion of said distance, there being a bore extending from one end of said recess through said wall means to an access opening at the outside, a removable closure for said access opening, and an elongated sound wave absorptive body inserted into said recess through said access opening and bore. 7

3. The subject matter of claim 2, wherein the sound wave absorptive body includes a resilient stiffening wire extending longitudinally through said body by which the body can be conveniently inserted and removed.

4. The subject matter of claim 2, wherein the sound wave absorptive body comprises a porous elongated casing, sound wave absorptive material in said casing, and a resilient stiffening wire extending longitudinally through and fixed to said casing and body.

5. In an internal combustion engine having an engine block formed with a cylinder and having a top face intersected by said cylinder, and a head having a bottom face seated on said engine block face, said head formed with a combustion chamber over said cylinder, detonation suppression means, comprising: an arcuate recess sunk into said bottom face of said head outside the perimeter of said combustion chamber and extending for a substantial distance around said combustion chamher, a restricted sound wave passage from said chamber into said recess extending lengthwise of said recess, and an elongated body of sound Wave absorptive material lodged in said recess. v

6. The subject matter of claim 5, wherein there is a bore in the side of the head leading to an end of said recess and through which said absorptive body can be inserted and removed, and a removable closure for the outer end of said bore.

7. The subject matter of claim 5, wherein there is a bore in the side of the head leading to an end of said recess and through which said absorptive body can be inserted and removed, and a removable closure for the outer end of said bore, and wherein said body has a resilient stiffener wire extending longitudinally therethrough and fixed thereto, said wire protruding from one end of said body to form a handle by Which the body can be inserted and removed,

8. In an internal combustion engine having an engine block formed with a cylinder and having a top face intersected by said cylinder, and a head having a bottom face seated on said engine block face, said head formed with a combustion chamber over said cylinder, detonation suppression means, comprising: an arcuate recess sunk into said bottom face of said head outside the perimeter of said combustion chamber and extending for a substantial distance around said combustion chamber, a shallower arcuate recess sunk into said bottom face of said head between said first mentioned recess and said chamber to form, with said top face of said block, a constricted sound wave passage from the combustion chamber to the first mentioned recess extending lengthwise of the latter, and an elongated body of sound wave absorptive material lodged in said first mentioned recess.

9. The subject matter of claim 8; wherein there is a bore in the side of the block leading to an end of said first mentioned recess and through which said absorptive body can be inserted and removed, and a removable closure forthe outer end of said bore.

References Cited in the tile of this patent UNITED STATES PATENTS 

